1. Field of the Invention
The invention relates to a method of producing a hollow monobloc body by expanding a parison made of a thermoplastic material using a blowing process, such as extrusion-blowing or injection-blowing, the body having a further element dispoed on one of its interior walls.
There are numerous cases where it is necessary to provide a further element inside a hollow body, either as a characteristic feature of the body or as a point of attachment or connection to the interior wall. When the hollow body is formed from two shells or two complementary members, such as a metal container formed by stamping or a container produced by injection moulding, it is convenient to put in place a further element which will form the desired projecting portion and to fix it to the inside of one of the shells before closing the assembly. It is not possible to use this method for one-piece containers by expanding a soft hollow parison of thermoplastic material as the size of the further element does not allow it to be introduced inside the hollow body through one of its original orifices.
2. Description of the Prior Art
It has been suggested to place the further element into the mould before the blowing process and to keep it spaced from the walls of the parison by means of a retractable support or mandrel, see, for example, French Pat. No. 1 317 649 in the name of Kautex. The further element can consequently be fixed to the interior wall after the blowing step. In all known cases, such as in the patent cited hereinbefore, the element is fixed by utilising a hole through the interior wall or the hole left behind by the support or the mandrel.
The hollow body is often used as a container or reservoir which must be air or water-tight. There is no guarantee that the spot where the element passes through the wall of the container or the reservoir is properly sealed and even less where the hole is made by the mandrel. Such a risk can not be taken as the container or the reservoir may have to be used for inflammable liquids.